Oil shales, particularly the Devonian-like shales of the Eastern United States contain organic carbon equal in amount to that contained in the Western shale of the Green River formation. However, upon retorting by the usual processes, Eastern shales yield smaller amounts of oil or hydrocarbonaceous material than the Western shales.
Several procedures have been proposed to enhance the yield of oil from Eastern shales. Previously known technologies relating to the recovery of organic material from rock, such as kerogen from oil shale, rely principally upon either thermal means or the use of molecular hydrogen and treat the rock in a substantially dry state, i.e., in the absence of any significant amount of liquid. See, for example, DT-OS No. 2,806,806 to Kraftwerk Union AG and The IGT Hytort Process for Hydrogen Retorting of Devonian Oil Shales by S. A. Weil at al., a paper dated Nov. 14, 1978 and presented at The Chattanooga Shale Conference. Such processes require the system transport of essentially dry rock and/or require the extensive use of inherently dangerous hydrogen gas.
Green et al., in U.S. Pat. No. 4,325,803 disclosed a method for removing organic material from oil bearing rock. According to the invention, rock containing organic material was contacted with a hydrogen transfer agent which was liquid at standard conditions by forming a slurry of the rock to be treated and a liquid comprising such a hydrogen transfer agent. In a preferred embodiment of the invention, rock containing the organic material to be separated, such as oil shale, was pulverized, preheated via contacting with hot recycle vapors and slurried with a liquid comprising a hydrogen transfer agent. The slurry was then reacted at elevated temperature and pressure and the product of the reaction flashed.
Patzer in U.S. Pat. No. 4,238,315 issued Dec. 9, 1980 disclosed another process for obtaining oil from oil shale. In his process oil was recovered from oil shale and a solvent at a temperature in the range of about 385.degree. to about 440.degree. C. and a pressure in the range of about 250 to about 2,000 pounds per square inch gauge (about 1.72 MPa to about 13.8 MPa) for a period of about 20 minutes to about two hours and thereafter recovering the resulting oil.
It has been observed when a H-donor solvent is used to modify an oil shale, a material is formed that is soluble in a variety of solvents. Prior to H-donor treatment, little or no solubility is possible. It has also been observed that not all solvents dissolve all the modified organic product. For example, it has been observed that whereas normal n-heptane dissolves about 50-70% by weight of the organic product of H-donor treatment, pyridine dissolves 100% by weight.
Therefore, what is needed is a process which will provide for the sequential selective solvent extraction of modified organic product remaining on H-donor treated oil shale, and a hydrogenation of extracted products to improve the efficiency and yield of products of oil shale, particularly Eastern oil shale.